The therapeutic use of human neural stem cells (hNSC) to treat neurological disorders or injuries depends upon the ability to direct stem cell differentiation into the relevant cell types, with the same overall architecture as the corresponding in vivo tissue. Gradients of biological molecules, called morphogens, are pervasive throughout human development and help direct cell differentiation as well as the position of different cell types within the fully formed human. In the early cerebral cortex, FGF-2 gradients are thought to have an important role in establishing the cell types and tissue architecture that are essential for ultimate biological function. Capitalizing on recent advances in microfluidic technology, we will apply different FGF-2 gradients to hNSC cultures to examine if FGF-2, when presented as a gradient, can induce hNSCs to recapitulate in vitro the various cell types and tissue architecture observed in vivo. Time lapse phase and fluorescence microscopy will be used in conjunction with immunocytochemistry to examine the effects of FGF-2 gradients on cell cycle, fate, size, position, proliferation, and migration. We predict that with the appropriate FGF-2 gradient, high FGF-2 regions will contain mostly mitotic hNSCs that divide symmetrically to form more mitotic hNSCs. Regions with slightly lower FGF-2 concentrations will be populated with more asymmetrically dividing hNSCs that begin to generate neurons. Regions with yet lower FGF-2 concentrations will generate only neurons, where local FGF-2 concentration causes hNSCs to generate neuronal cell types specific to certain layers of the cortex. The study that we have proposed is the first to investigate a specific event in human development by culturing human stem cells in a microfluidic device that recreates the types of chemical microenvironments observed within the developing fetus. We believe the proposed study will yield great insight into human neural development and will make a significant step forward towards developing functional in vitro neural tissue from human stem cells. PUBLIC HEALTH RELEVANCE Understanding how the part of the brain that gives humans their unique cognitive abilities initially forms is important for understanding the cause of many disorders and diseases of the brain. The ability to direct stem cells to replicate the types of cells and the arrangement of those cells observed within the human brain would greatly advance our ability to treat brain disorders, diseases, and injuries. [unreadable] [unreadable]